A variety of inspection methods have been designed to inspect three-dimensional features of manufactured objects using a spot and/or a line laser. For relatively simpler three-dimensional object features, these methods measure height differences of the three-dimensional objects. To measure complex three-dimensional object features, these methods require complex algorithms and long measuring times to process the data and determine whether the object meets the manufacturer's specifications.
In systems employing a spot laser, a laser beam is moved to a different location of a target to perform measurement. A sensor provided in such systems measures only one point at a time. Measurement may be of for example, the location of the maximum intensity of reflected light on the sensor that may in turn indicate the height of a specific point on the three-dimensional object. Therefore, the number of points measured is limited and the movement of the spot laser between two points is slow. The disadvantage of these systems is that the target location must be known precisely before inspection. Further, the three-dimensional feature and/or dimension information retrieved may be very limited and error-prone due to positional errors.
In systems employing a line laser, a laser line is projected across a target. The laser line is moved across the target to scan the target and information is collected to perform measurement of three-dimensional surface of the target. Specifically, a line profile cross section of the target may be measured at each position. Within the line profile, relative regions within the line can be measured with high accuracy. The disadvantage of these systems is that the position of the target in the moving direction must be known precisely before inspection. Further, computing three-dimensional features and/or dimensions on the line profile while scanning the target needs long computation times as such systems require complex three-dimensional algorithms to process the data. Even though the number of points measured may be improved but the measuring speed is slow.
Thus, there is a need for a system/method to inspect the three-dimensional features and/or dimensions of a three-dimensional object in a simple and efficient manner.